As a conventional technology, there has been proposed a rotation angle detector that reduces an influence of magnetic noise on an output signal when detecting a direction of a rotating magnetic field (e.g., see JP 2007-10449 A).
A rotation angle detector disclosed in JP 2007-10449 A or JP 2016-514833 A has a sensor disposed with a pair of magnetic detection elements in a plurality of directions with respect to a rotating magnetic field, and a signal processing part that processes a signal output from each magnetic detection element of the sensor and outputs a signal corresponding to an angle of the magnetic field. In the rotation angle detector, the signal processing part specifies an influence of magnetic noise by comparing a phase and an amplitude of each output of the pair of magnetic detection elements when the magnetic field is rotated, and outputs a signal with reduced influence of magnetic noise by subtracting the influence of the magnetic noise, or by performing calculation processing such as averaging individual outputs of the pair of magnetic detection elements.
However, although the rotation angle detector of JP 2007-10449 A or JP 2016-514833 A outputs a signal with reduced influence of magnetic noise, it is necessary to arrange magnetic detection elements in a plurality of directions with respect to the rotating magnetic field, causing a problem that a shape of a sensor cannot be made smaller than at least a region where the magnetic detection elements are disposed. In addition, it is necessary to make a rotation centre of the rotating magnetic field substantially coincide with a centre of the rotation angle detector, causing a problem that an arrangement of the rotation angle detector is limited.
Hence, there is a need for a rotation angle detector wherein at least one of these drawbacks is avoided or overcome.